During the processing of hog carcasses, certain bacterial contaminants are introduced or are otherwise associated with the meat that subsequently impact the safety and storage life (spoilage) of pork products. Typically hog carcasses are subjected to scalding in preparation for dehairing. The scalding process comprises spraying with, or submerging the carcass in, hot water (typically about 60.degree. C. for several minutes). This conditions the skin for the dehairing process. The carcass is then singed and scraped (polished), typically with rubber flails, to remove the last vestiges of hair. These steps are conducted prior to eviscerating the hog carcasses. The scalding process is inherently lethal both to most bacteria hazardous to human health and to most bacteria generally responsible for spoilage. Unfortunately, traditional mechanical means used for the actual dehairing and scraping processes are not sterile and reintroduce and contaminate the carcass with pathogenic and spoilage bacteria. During the dressing and fabrication of hog carcasses, bacteria are transferred by the hands of workers and by equipment from the carcass skin to the meat products. Opportunistic spoilage bacteria, which survive the processing, thrive and multiply in the post-processing environment (chilled storage), reducing the storage like and the end products. There are health and commercial benefits which result from decreases populations of pathogenic and spoilage bacteria on meat including: increased safety; increased storage life; improved resistance to the subsequent effects of variable storage and shipping conditions; and compliance with strict foreign importing requirements.
The transfer of bacteria from the skins of animals to meat is also a major hygienic problem in processing other animal carcasses such as sheep and cattle carcasses from which the skin has been removed during dressing. The hygienic condition of flayed carcasses can be improved by using flaying techniques which avoid contact between the outside of the hide and the meat. However, bacterial contamination cannot be wholly avoided. A means of removing or destroying the bacteria on skinned and/or eviscerated carcasses is needed.
In general, destruction or inactivation of bacteria may be accomplished by the process of pasteurization. Pasteurization, as the term is applied in the food industry, is a process by which a very high percentage of a food borne population of microorganisms is killed or rendered incapable of reproduction by raising the internal temperature of the microrganisms to a lethal or critically damaging level in a controlled way (usually by holding the temperature of the microrganisms at a fixed temperature for a fixed time). In contrast to food sterilization processes, more care is given in pasteurization to the inherent sensitivity of the food product to heat exposure to provide an optimum balance between the level of microbial destruction and thermal alternation of the food product. A low-temperature, long-time pasteurization process can achieve the same level of microbial destruction as a high-temperature, short-time process, but the effect on the food product will be vastly different. Negative alteration of the carcass meat (cooking) is minimized by selecting short exposure times at higher temperatures.
The prior art discloses several systems for washing, scalding or decontamination of carcasses prior to refrigeration. Proposals for decontamination include washing dressed carcasses with solutions of chlorine (Kelly et al., J. Appl. Bacteriol. 51 (1981) 415.) or organic acids (Hell et al., J. Food Prot. 49(1986) 207 and Woolthiusetal, J. Food Prot. 48 (1985) 832.), and heating carcass surfaces to pasteurizing temperatures with infrared heater (Snijders et al. Fleischwirtsh 57 (1977) 2216-2219), water sprays (Kelly et al (1981)) or sheets of water (Davey and Smith, Int. J. Food Sci. Technol. 24 (1989) 305). Simple cleaning of carcasses with water using an oscillating system of sprayers is proposed by Anderson in U.S. Pat. No. 4,337,549. A hot spray scalding apparatus for fowl carcasses is proposed by Harben in U.S. Pat. No. 4,868,950. Most of the prior art proposals process animal carcasses that are moving on the overhead dressing rail. Removal of carcasses from the rail is operationally inconvenient and economically disadvantageous.
In U.S. Pat. No. 4,965,911 to Davey and in U.S. Pat. No. 3,523,326 to Ambill, systems are disclosed in which heated water is directed onto carcasses. These references use differing approaches for delivering heated water to the upper, lateral and convoluted areas of carcasses. These areas are often times shielded from the direct line-of-sight trajectory of the water issuing from the distributing means.
The Davey apparatus is designed for treating dressed beef sides. A plurality of longitudinally aligned vertical sheets of heated water (83.5.degree. C.) are introduced from an overflow weir-type water distributing means above the carcass. In order to adapt to convoluted surfaces on the lateral surfaces of a carcass, Davey requires a plurality of baffles positioned at various elevations on either side of the carcass. The baffles impinge the vertically descending sheets of water and deflect them laterally to somewhat better contact the carcass's lateral surfaces. Changes in the size and geometry of the carcass requires manual repositioning of the baffles. Furthermore, the use of deflecting baffles has the tendency of breaking up the descending sheets of water.
In Ambill's apparatus, carcasses are scalded prior to dehairing, using heated water (about 60.degree. C.) introduced from distributing means located on either side of the carcass. The water is deflected laterally under no pressure to contact the lateral areas of the carcass. The deflected water is shown in the patent drawings (FIGS. 4 and 11) as a weak, broken flow or spray falling downwardly onto the carcass. The point of discharge of the distributing means is close to the carcass and vertically movable to oscillate between upper and lower positions, thereby accessing the vertical extent of the carcass. A mechanically complex framework is required to enable the vertical movement of the Ambill's water distributing means. Also, the oscillating, vertical movement of the water distributing means provides only intermittent wetting of portions of the carcass surface. The oscillating vertical movement also contributes to the spray like pattern of the water trajectory.
The rails and carcass suspension means of both the Davey and Ambill apparatus pass within their respective housings, introducing greases and contaminants associated with prior processing stages and the conveying system.
There is a need for a carcass pasteurization cabinet which accepts carcasses of variable geometry without significant modification, uses simple componentry, and yet provides effective pasteurization of the surfaces of the carcass.